When Normals aren't so Normal

Required Software: Blender 3D, Photoshop (GIMP is fine too)

Have you ever attempted to improve the efficiency of your 3D Models with Normal maps, only to be met with the disappointment of:

  • Missing Geometrical Details
  • Green Artifacts
  • Broken Seams
  • Inconsistent patterns
Reducing these details can require a multitude of solutions for clean, visually accurate surface detail, while reducing vertex count. This can be paramount to ensuring for perfomance and effeciency in real-time 3D engines, especially when intended for Rigging & Skinning bones.

Before you start baking: Make sure that in your active mesh, your normal map is unconnected and the texture is selected (white selection line). Missing this will cause a Circular Dependency error and Texture not found.


While creating the high-to-low-poly mesh this is a particular problem as the circumstances for each Texture Bake has different mesh translations. Take this Normal Bake for example:





When using "Selected to Active" to translate the detail from high to low, the Metal Brass details have the appearance of visual artifacts, which render as if the face normals are inversed. What is this Green artifact? 

Every UV Map has a portion of Green-Cyan colour in its composition. The green represents the Y axis on the axis of normal maps. Red and Blue represent the X and Z axis (Adobe, 2025). The default Purple on normal maps derives from the blend on Red + Blue, representing a flat plane.

Fun Fact: Although normal maps are generally used for real-time graphics engines, 3D animation studios like Pixar's Renderman (Pixar, 2025) utilise Normal, bump and Displacement maps to reduce rendering time.

So if there is no green the texture has no height. But if there is a solid block of green the max value of Y is active. We can mitigate this issue through the "Selected to Active" Bake Settings found in render settings(Camera Symbol).



Extension: Increase and decrease the extrusion from the surface position. Where the middle of the scale is. Recommended value: 0.015m (only if you have artifacts)

May Ray Distance: This adjusts how far the Ray detects your baked details. Think of this as the range of captured geometry to turn to detail is. Recommended default value: 0.1m

Changing these two values can effect each others outcome, so some tweaking is required to get optimal results.



Fig.3 Quick sketch of how the two settings work in practice.

My Normals still look Artificial/Glitchy

If Blender fails to remove all the visual artifacts, you may need to manually correct the normal values. if you have non-conventional geometry with convex shapes, this will be more likely. See below in Fig 4 & 5. No worries though as we can edit normal maps using photo-editing software.

Fig, 4. First try with high poly mesh render bake.

Fig 5. After Adjusting the render values, the normals are still incorrect .

After rendering, View the  the output of the normals in 3D first (It can be difficult to interpret normals purely through UV Maps).

Fig.6 Green Spots in normal map appear in render as black artifacts

If your rendered result isn't as intended, you can try the following in Photoshop or equivalent photo editing software:


Green Artifacts - If the visual glitch is in the same area, select that specific area, then Filter > Invert.

Unwanted geometry -  Use Eyedropper to change your Brush to the Default Plane value or the local 

Partially Correct Details - We know Normal Maps are just representations of XYZ values, and just Free Transform & Shear to duplicate existing correct detail. However, you cannot rotate your selection. 

This also helps with duplicating intricate detail to save valuable time!

Inconsistent Normal Values: When tweaking Extrude & Max Ray Distance values, if the normal map  combine multiple normal maps to achieve your intended effect.




Fig.7. Cleaned Up Normal Maps after utilising all the advice included in this post.



Still Having Problems?

If your Normal map output is so unrecognizable from the orignal high polygon mesh, you may have corrupted or non-standard geometry. (Common when using lots of Modifiers) (Loose Edges, 2023)

Try these quick tricks to standardise your geometry:

Remove Doubles - In Edit Mode, select all geomtery (A ) then Press M

Recalculate Normals - Press Shift-N

Non-Manifold Edges - In Edit Mode (Must be selecting edges or vertices) go to Select > select All by trait > Non Manifold



Good Luck & Happy Modelling!


References:

Adobe, 2025, What is Normal Mapping https://www.adobe.com/uk/products/substance3d/discover/normal-mapping.html

Pixar Renderman, 2025, Pixar's RenderMan Fundamentals http://renderman.pixar.com/fundamentals-patterns

Loose Edges, 2023 "How to Fix Normal Map Artifacts - A Blender Tip or Two" https://www.youtube.com/watch?v=_KAdfKj_bEg

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